High integration of a semiconductor device has been achieved by adoption of the fine process and improvement of the mounting density in a two-dimensional LSI (Large-Scale Integration). In recent years, however, physical limitations of the microfabrication have come within sight, and a three-dimensional LSI has drawn the attention.
In the three-dimensional LSI, a semiconductor device is formed in such a manner that substrates on which devices having various functions (for example, a memory device, a logic device, and an image sensor device) are formed are bonded with each other, and thereafter an upper-layer substrate is thinned down to a desired thickness using a grinding process (for example, see Japanese Unexamined Patent Application Publication No. 2011-96851 (PTL 1)).